good day

last nite i took my 140 off my patern ship and as i started to turn the crankshaft i heard a hiss from the exhaust outlet ... basicly what is happening is that my valves are not air tight !!! the engine is not rand new ... nore very used ... any suggestiong on what i should do ??? sending it off to servie is not an option becaue i am not in the us ...

thank you

Hi,

... since Troy is gone for the moment, and asking us to answer this topic, i have an suggestion to your problem ...

I guess you have already checked the valve clearance .. if not .002 " is a good starting point ...

What we have seen is carbon build-up around the exhaust-valve stem, causing the valve to stick in the guide,preventing the valve to return in the valve seat ( Often felt as low-or no compression )... carbon build-up in the valve-seat can more likely be the cause if the compression is good and you suspect some small leakage...

What you can do is disassemble the valve, put the vale-stem into a dremel-machine, and use a soft material ( like aluminium ) to remove the carbon ...

The DZ head is really good regardarding the valve seat, and basically the problem are often related to the carbon build-up to the exhaust valve ...

Hope this help

Kjell Olav.

thats the bigest problem i have already cleaned the walve ... and the place where it sits is nice and shiny just like on my os 120 ... but there is still plenty of leakage

I would recommend lapping the valve. It will re-hone the valve and seat to match up and seat properly.

The way the YS valves are made is very cool. They will be self fitting. What happens is the valve is a softer stainless steel. What happens is under heat and compression the valve will eventually seat within just a few runs. So if you just had it all apart and put it back together...Run it and see if it comes back. I only start looking at these things as being wrong if the engine is not working properly. The valve will seat as long as everything is clean and clear. It make take a few runs. But they usually do. We tried shaping the the valves years ago on the 120AC to make it more efficient. After just a few runs the shape of the valve was the same as the seat again.

You can lap the valve with tooth paste or a very fine lapping compound and a dremel tool on slow slow speed. You need to remove the valve retainer springs and all from the valve and it must turn free in the valve guide. I totally strip the head down and remove all parts...as I don't want the lapping compound to be gritty and get into other areas. I use a pencil eraser in the dremel tool. I then push down on the flat of the valve and rotate it say 60-80rpm for short periods of time say 10 secs. Then clean it all up with denatured alcohol and do it again with fresh lapping compound. Like I said old fashion tooth paste works great for this application. After you are done...clean all the parts really good with Denatured Alcohol and re-assemble. Its a pretty easy process but like I said I rarely do it. Usually a few runs and its all good to go.

Now if carbon is present this will affect things...the main reason we don't run Castor oil in our engines is this carbon problem. Still there is some small amount of build up even with the CP 30% heli. This is a dry build up that is pretty thin. It can be an issue over long term but it takes hundred and hundreds of flights Like 500-600 before it becomes and issue. There are other fuels that on the market that tend to build up very fast.

I like Posted I'm leaving for at least a week. If you have any questions these guys can help you out.


Troy Newman
Team YS